Convicted of murder, jailed for three years and then finally acquitted, Gordon Wood is suing the state of New South Wales for malicious prosecution and wrongful imprisonment.

Mr Wood spent more than three years behind bars after being convicted of killing Caroline Byrne, his then girlfriend, by throwing her off a cliff at notorious Sydney suicide spot The Gap in June 1995. His conviction was overturned in 2012.

So, what does he have to prove for his current case to succeed?

"Malicious prosecution is a civil suit that you can bring and there are broadly four elements to it," Professor David Rolph from the Sydney Law School at the University of Sydney said.

"The person [or body] that you are suing has to have prosecuted you, usually for a criminal offence, and that prosecution has to have been terminated in your favour.

"Then you have to prove that the person who prosecuted you acted with malice, which is improper motive, and that the prosecution against you was brought or maintained without reasonable and probable cause."

Professor Rolph said establishing all of those elements can be difficult.

"Because the onus of proof rests with the person suing, there's a high degree of difficulty, particularly in relation to that element of malice," he said.

"If the prosecution can demonstrate that they were simply invoking the ordinary processes of the criminal law, then that is usually sufficient to prevent a plaintiff from proving malice."

Difficult to prove, but not impossible: expert

In 2015, Roseanne Beckett won her case for malicious prosecution, after being wrongfully convicted of plotting to kill her husband in 1991 and spending 10 years in jail.